The multiplicity of orbitals in quantum systems significantly influences the competition between Kondo screening and local spin magnetization. The identification of orbital-specific processes is essential for advancing spintronic devices, as well as for enhancing the understanding of many-body quantum phenomena, but it remains a great challenge. Here, we use a combination of scanning tunneling microscopy/spectroscopy and electron spin resonance (ESR) spectroscopy to investigate single iron phthalocyanine (FePc) molecules on $\mathrm{MgO}/\mathrm{Ag}(100)$. We observe the coexistence of ESR and Kondo resonance from the Fe(II) ion center at a temperature well below the Kondo temperature $T_{\mathrm{K}}$, where the magnetic moments are determined to be 1 Bohr magneton ($1{\mu }_{\mathrm{B}}$), corresponding to a spin $S=1/2$ state in either of the ESR and Kondo resonance channels. On the basis of the observed in-plane twofold symmetry in the spatial distribution of ESR linewidths, in combination with density functional theory calculations, we attribute one spin $S=1/2$ state in the degeneracy-lifted $d_{\pi }$ orbital to the ESR channel, and the other in the highly screenable $d_{z^2}$ orbital to the Kondo resonance, respectively, within the framework of the $S=1$ two-channel Kondo model of an ordinary Fermi liquid.

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• Electronic structure of atoms & molecules
• Kondo effect
• Density functional theory
• Electron spin resonance
• Scanning tunneling microscopy
• Scanning tunneling spectroscopy